CIS fuel pumps, how much HP?

[Dupree, Jim]

I would add one caveat. You can get too much fuel volume for your fuel
pressure regulator to handle at idle. Since the engine does not use much
fuel at idle most of what your pumps will be doing is recirculation the fuel
through the system and back to the tank. We ran into this on a 911 turbo
project car (428 hp on an engine dyno). MoTec fuel/ignition running 2 fuel
pumps to insure enough fuel under full load at high rpm. The fuel pressure
would creep up at idle causing and overly rich condition. We had to add a
second pressure regulator and return line to control it. Maybe we went a
little over board on fuel pump sizes but we never had a lack of fuel.
Jim
1984 4kq
1985 4kq

-----Original Message-----
From: JShadzi at aol.com [mailto:JShadzi at aol.com]
Sent: Tuesday, November 26, 2002 11:28 AM
To: jeg1976 at yahoo.com; quattro at audifans.com
Subject: Re: CIS fuel pumps, how much HP?


IME, the CIS3 pump is good to 400hp safely, I just replaced my 15 year old
CIS3 pump recently because I was getting some fuel cut out at 20psi and race
gas (350+hp I'd say no problem, considering I have about 300 at 15psi),
swapping in a S. African CIS truck (Eurovan) pump seemed to do the trick,
its the same diameter as the CIS3 pump, but 1" longer, a real hog, got it at
Eurospec a way back, no more cutting out.

Anyway, you can't go wrong with 2 pumps, maybe a little overkill for 350hp,
just keep an eye on your fuel pressure, if it drops at max power, you know
you need more pump.

Javad
80tq.com

>In preparation for some obscene HP, I've been
>wondering how much HP the CIS-III fuel pumps are good
>for?  I'm planning on trying for 350 hp after the
>header and new IM go in.  Should I pipe in a second
>pump in parallel just to be safe?  It's already
>sitting right there from the first stage of the
>project.  As far as the header goes, it just went to a
>new welder as the first one was just to backed up to
>do it anytime soon.  He said maybe Friday!  I can't
>wait to get my car back..
>
>TIA,
>
>=====
>Jim Green
>'89 90tq 034EFI, Haltech IG5
>http://www.geocities.com/jeg1976/car_home.html
>
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